1. Field of the Invention
The present invention relates to a transmission method for physical layer low power communication and an apparatus for the same.
2. Description of the Related Art
Recently, wireless local area network (WLAN) standard continues development to support a wider service area than the past and support a ceaseless service in a moving environment in which a movement speed is much increased in comparison to the past. According to institute of electrical and electronics engineers (IEEE) 802.11a/b/g standard, data transmission at a physical layer data rate maximally of about 54 Mbps using a bandwidth of about 20 MHz in a 2.4 GHz or 5 GHz band via a single antenna is enabled. According to IEEE 802.11p, data transmission in a fast moving vehicle is supported in a 5 GHz band at a data rate up to maximally about 27 Mbps based on an IEEE 802.11a physical layer.
In IEEE 802.11n standard, a plurality of antennas are used by applying a multiple input multiple output (MIMO) technology and a bandwidth up to about 40 MHz is supported, thereby supporting a physical layer data rate of about 600 Mbps. IEEE 802.11ac standard supports a data rate to transmit a gigabyte per second using maximally eight antennas and a bandwidth of about 160 MHz. In particular, the IEEE 802.11ac standard enables a single access point (AP) to transmit data to a plurality of users simultaneously, by applying the MIMO technology.
As a next generation WLAN standard following IEEE 802.11ac, high efficiency WLAN standard for increasing efficiency of the conventional WLAN has been discussed in an unlicensed band of 2.4 GHz or 5 GHz. Whereas the conventional WLAN shows a low efficiency with respect to a technical performance due to interference, high efficiency WLAN (HEW) which is the next generation WLAN standard is expected to show high performance in view of throughput, delay, and energy efficiency. A method for increasing spectrum efficiency and network throughput in an environment crowded with APs and stations, which is a mainly considered scenario, has been actively discussed.
As smart devices are popularized, users of the mobile internet are continuously increasing. With an increase in real time traffic such as high capacity multimedia, for example sound, image, and the like, a bandwidth and speed of a network device for accepting the traffic are also increasing. With rapid spread of high performance intelligent mobile terminals, demands of the users are continuously diversified and increased.
However, energy consumption is increasing in proportion to a performance increase of the network device. Since wireless communication devices equipped with a high communication technology use a strong processor, an affluent memory, a wide screen, and an open operation system (OS), an energy budget of a wireless communication interface with a limited battery capacity should be extremely limited.
Wireless communication systems are rapidly developing to accept additional elements and technologies to add new functions and increase the performance. However, development in a battery size and a battery capacity is relatively slow. Accordingly, in regard to the wireless communication systems, there is a desire for a method for using the limited battery capacity longer and more efficiently.
Due to a limited power capacity of a wireless communication mobile terminal, a research for reducing the energy consumption is actively conducted. In particular, it is known that, in mobile devices such as a smart phone, a tablet, a notebook, and a sensor, most of energy is inefficiently consumed in the wireless communication interface. Since the battery capacity is limited in the mobile terminal or the sensor, a technology for minimizing energy consumption is necessary.
In a mobile node, most of energy is consumed in a central processor unit (CPU) and the wireless communication interface. The CPU may reduce energy consumption by variably controlling a clock frequency and a voltage supply according to a load to be processed and requirements of an application program. That is, when the CPU is operated at a low frequency and a low voltage or when a task to be processed is absent, the operation may be suspended until the task is generated.
A wireless interface may reduce power consumption by two methods as follows.
1) The wireless interface is awake only when there is data to be exchanged with another wireless device. Otherwise, a power save mode is maintained to reduce energy consumption.
2) When a received packet does not correspond to an identifier (ID) of the wireless interface, data processing is not performed to reduce energy consumption.
However, according to the foregoing technologies, the efficiency may be deteriorated since an environment and condition of a mobile node are not considered. In a conventional wireless modem physical layer, energy consumption has been reduced by setting a maximum operation frequency to be low, by minimizing a voltage supply or decreasing complexity, and by variably controlling the clock frequency and the voltage supply according to the load to be processed.
However, reduction in the operation frequency, the voltage supply, and the complexity is limited with a conventional semiconductor processing technology. Since those three factors are in trade-off relationships with the performance, meeting of performance requirements of the system is limited.